1. Field of the Invention
The invention is in the field of hydrocarbon waste disposal. More particularly, the invention relates to a landfarming medium and process in which waste hydrocarbons are oxidized by microorganisms.
2. Description of the Prior Art
It is well-known that hydrocarbon-utilizing microorganisms are ubiquitous in soil. These microorganisms use hydrocarbons as an energy source for their life processes and frequently as a source of cell structural materials. The reactions by which the organisms metabolize hydrocarbons are enzyme-catalyzed oxidations involving dehydrogenation of the hydrocarbon substrate. The process is called aerobic metabolism when the hydrogen atoms generated in the reaction are combined with oxygen to form water and anaerobic metabolism when the hydrogen atoms are combined with hydrogen-accepting moieties other than oxygen, such as nitrate or sulfate. The ability of microorganisms to oxidize hydrocarbons has been used widely to treat hydrocarbon-containing wastes.
The patent literature describes various microbial processes for disposing of hydrocabon wastes. U.S. Pat. No. 3,152,983 describes a process for treating aqueous hydrocarbon-containing wastes by adding a microbial sludge to the waste and aerating the waste. The microbes oxidize the hydrocarbons in the waste. U.S. Pat. No. 3,224,946 teaches a process for enhancing microbial attack of hydrocarbons in an aqueous medium. The enhancement involves adding finely divided zeolitic molecular sieves to the medium. The hydrocarbon substrate is absorbed by the sieves, thus dividing it into small occluded particles and facilitating its oxidation by the microbes in the medium.
U.S. Pat. No. 3,616,204 concerns a technique for treating accidental oil spills on soil by tilling the oil into the soil, inoculating the soil with a hydrocarbon oxidizing microorganism, and adding nutrients to the soil and maintaining its oxygen content to stimulate microbial oxidation of the oil. U.S. Pat. No. 3,843,517 relates to a similar technique for eliminating oil slicks on bodies of water. The technique involves dispersing lyophilized cultures of oil-consuming microorganisms adsorbed on porous carriers in the oil slick.
The ability of soil microorganisms to consume or ferment hydrocarbons is also used to dispose of hydrocarbon wastes in a process called "landfarming" or "land spreading". In landfarming the hydrocarbon waste is tilled, injected or otherwise incorporated into the soil. Once in the soil, the hydrocarbon is oxidized by soil microorganisms into innocuous products such as carbon dioxide, water, and humus. It is often necessary to till the soil frequently to aerate it to provide the oxygen necessary for the fermentation. The main problem with current landfarming is that it requires a substantial land area for a substantial time period to dispose of a large volume of hydrocarbon. There is, therefore, a great need for increased biodegradation rate in landfarming so that less land area is required per unit amount of disposed hydrocabon. The present invention is directed to filling that need.